This invention relates to balloon catheters and more particularly to balloon angioplasty catheters having therapeutic compounds releasably attached to a balloon.
Dilatation balloons on catheters are well known in the art and are used to decrease the restriction caused by plaque within a vessel wall. Plaque varies greatly in consistency and may be anything from a soft fatty tissue to a harder calcified material. In either case, it is often desirable to do more than simply force a balloon against the plaque or other restriction in the hopes that any plaque and vessel wall may be stretched to open the lumen more fully. Laser angioplasty uses lasers to vaporize the plaque at the stenosis, while atherectomy uses cutting actions to remove the plaque.
Researchers are currently screening a number of drugs to limit or dissolve plaque and to limit the growth of neointimal tissue. Unfortunately, such compositions have been difficult to apply directly where needed. Instead, such drugs tend to be applied systemically which essentially treats portions of the body which need no treatment. Also, such treatments mean that the dosage to the body must be quite high to insure that the localized area having a need for treatment will receive adequate drugs.
Concentrated heparin is delivered by a perforated balloon catheter in work by Wolinsky et al, as described in European Patent publication 0 383 429 of C. R. Bard, Inc. The drug is sprayed through minute holes in the balloon. Also see JACC Vol. 15, No. 2, February 1990: 475-81 by Wolinsky et al.
The assignee of the present invention has filed a patent application entitled "Intraluminal Drug Eluting Prosthesis", Ser. No. 07/486,580, filed Feb. 28, 1990 which places a stent bearing drug at the location desired. Other attempts have involved an application of catheters having separated balloons and the introduction of the drug from an internal lumen of the catheter to the space formed between two inflated balloons. Obviously, this procedure requires the introduction of drug through a lumen within the catheter meaning that the volume of the drug is quite high. Also, if the plaque is badly fissured there will not be a complete seal between the two balloons and the drug will escape to other parts of the body through the vessel. Also, the time available for treatment with such a system is quite short since the balloons must eventually be deflated to allow blood to flow.